Field
The present disclosure generally relates to spherical salt particles, and more specifically relates to methods of making spherically shaped, or nearly spherically shaped, salt particles for industrial, medical, culinary, or other uses.
Background
Crystals develop their crystalline shape due to the manner in which growth occurs along different crystallographic planes. For example, common salt, or sodium chloride (NaCl), naturally forms as cubic crystals.
Many industrial and manufacturing processes use sodium chloride. For example, the textile, dairy, food, fertilizer, paper, and pharmaceutical industry all use sodium chloride to some degree. The flow properties of salt are important in many of these applications. Natural sodium chloride crystals do not have ideal flow characteristics. For example, salt particles, when used in a fluid state, have a tendency towards agglomerations. This is partially due to the angular nature of salt particles.
For many industrial and other applications, it would be beneficial to improve the flow properties of salt particles. Generally, particles that are rounded or spherical in shape tend to behave with more fluidity than otherwise identical particles that are angular in shape. If salt particles were readily available in rounded or spherical form, many of the industrial processes that rely on them might be benefitted or improved because of improved flow properties. Even consumers of salt for flavoring of food may benefit from salt that more predictably or smoothly flows from its container.
Additionally, in the medical device field, salt can be used to create texture on medical implants, for example, textured breast implants. In this application, salt particles are used as a sacrificial material that is applied to a sticky or fluid elastomeric material, such as silicone. After application of salt, the silicone is cured or allowed to set or solidify. The salt particles are then removed, thereby revealing a silicone material having a textured surface. For these and other applications, it can be appreciated that it would oftentimes be desirable that the sacrificial salt used is as uniform in size and shape as possible, for example, in order to create a predictable and uniform porosity leading to more optimal weight/strength ratio of the product. Rounded or spherical salt particles for use as a texturing material may help to form a texture that has a less angular topography than a texture made using angular salt particles. For example, as disclosed in U.S. Pat. No. 8,313,527, the entirety of which is incorporated herein by reference, elastomeric silicone materials that are textured using rounded salt particles have improved physical properties, such as improved strength, relative to otherwise identical elastomeric silicone materials that have been textured using angular salt particles.
Several methods have been developed and are reported to produce rounded or spherical salt in the particle size range of common table salt (e.g., about 100 μm to about 500 μm). These methods include, for example, evaporative processes that change the crystal morphology of the salt (see EP1545733B9) and moltenizing salt crystals while suspended in hot air (see JP09086923A2). Other wet chemical methods are described in U.S. Pat. Pub. No. 2009/0176096 A1 and U.S. Pat. No. 7,220,435.
These and similar reported processes all require many steps and specialized equipment and may be difficult to scale up to large volumes. In addition, these types of processes can have low yields, and frequently use ingredients that reduce the purity of the resulting salt.